ALB and target Group : Health check failure

Question

Dear Team,

I am working on one ALB application , that DNS i mapped with my Godaddy credentials, my server also up and running , no issues anywhere but still my Target group status showing Unhealthy after few minutes of instance launched and getting drained and launching new instance, like this its repeating.
If i check my ASG , i gave desired, minimum and maximum capacity as '1' , but still before terminating the old instance its creating new instance once the other comes 2/2 checks passed, old instance getting drained by themself. so its not affecting my server running status anywhere
but still, without any load why this health check failure happening, if i open the target group attributes , there i can find 'DNS Failover + Fail Open' , what is that unable to find any solution for this
Please assist

Answer

Hello.  
Automatic scale-in and scale-out cycles when ALB target health checks fail.  
So, we must first configure the ALB health check to succeed.  
Points to check for basic troubleshooting are listed in the following documents.  
https://repost.aws/knowledge-center/elb-fix-failing-health-checks-alb

The following document describes how to check for EC2 problems in an AutoScaling group.  
Start EC2 from the startup template and check that the web server is running properly in the OS and that the application responds normally.  
Also make sure that the security group is set to allow access from the ALB.  
https://docs.aws.amazon.com/autoscaling/ec2/userguide/ts-as-healthchecks.html

ALB and target Group : Health check failure

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